I've left messages with Det. Judith McGee, who's handling the case and is out today. Other Central investigators to whom I spoke aren't sure, but DPD spokesman Senior Corporal Kevin Janse thinks maybe he can find out where that picture was taken. We'll update accordingly.

Update at 12:49 p.m.: Nailed it. Janse responds:

Those pictures were taken from the 7-Eleven store at 8402 Harry Hines. Those pictures will also be taken to the convention center to be shown to all of the different department managers to see if they recognize them as being employees of the convention center.